1. Technical Field
The present disclosure relates to a light emitting diode technology, in particular, to a manufacturing process for improving the yield rate of a light emitting diode and a light emitting diode structure using the same.
2. Description of Related Art
As the advancement of human civilization, lighting devices have becoming the essential component in the daily life. In the early days, the lighting devices in general are incandescent light bulbs (or tungsten lamps). Hence in the past, to have the lighting device dimmed, only need to arrange an additional variable resistor turning knob between the electrical plug and the lamp. Consequently, brightness may be configured by adjusting the variable resistor. However, the incandescent lamps have the disadvantages of heating, short lifetime, low lighting efficiency, and large power consumption thus currently has almost completely obsoleted.
A light emitting diode (LED) is a solid-sate light emitting component and mainly composed of the P-type and N-type semiconductor material, further may generate self-radiating lights within the spectrums of ultraviolet light, visible lights, and infrared lights. In practice, the light emitting diodes emitting visible lights are mostly used as indicator in electronic instruments or for illumination application while the light emitting diodes emitting infrared light are utilized in optical communication application.
As LEDs have advantages including high lighting efficiency, long lifetime, hard to be damaged, low power consumption, environment friendly, and small in size, hence recently under the trends of environmental protection and energy saving, it has been broadly used in many fields, such as traffic lights, streetlamps, torch lamps, backlights of liquid crystal displays, or all types of LED lamps.
The Distributed Bragg Reflector (DBR) often has been used in the nitride-based LED structure for enhancing the lighting efficiency of the light emitting diode. The gallium nitride (GaN) and aluminum gallium nitride (AlGaN) have large refractive index difference thereby have been commonly used in developing the DBR of gallium nitride component. However, the combination of these two materials may also bring great lattice mismatch and thermal coefficient differences, consequently may facilitate generating cracks or defects in the epitaxial layer.
Moreover, the stress issues of developing the DBR using the epitaxy may impact overall lattice quality further resulting in structural defects. Especially, the structure having the DBR may contain relatively large tensile strain and often causes the epitaxial layer formed afterward unable to effectively release the strain and generate cracks. In addition the LED structure growing on the silicon substrate always has the wafer strain problem leading to crack generation. Consequently to develop DBR structure using epitaxy method, the wafer must bear large tensile strain, thus may easily generate cracks.